A method for converting scanning values of an input scanning sequence to scanning values of an output scanning sequence is disclosed, for example, in European Patent No. 52,847. In accordance with the method in European Patent No. 52,847, scanning sequences are changed into scanning sequences with other scanning frequencies. The desired scanning values are determined by interpolating obtained scanning values. The interpolations are performed using interpolation filters.
However, the method of European Patent No. 52,847 has a number of disadvantages. For instance, the conversion method results in a converted signal that has an undesired noise signal of at least 3 db. The noise is attributed to the multiplication of the input scanning values with filter coefficients, and with a subsequent filter word length reduction. Furthermore, the quality of the output signal is reduced if the input scanning frequency and the output scanning frequency are not of an optimum quality. This may be caused, for example, by a poorly designed phase lock loop (PLL) circuit. In addition, the effort required for storing filter coefficients and the required logic for processing them can be considerable when certain input and output scanning frequencies exists.